The disclosed embodiments of the present invention relate to generating a clock signal, and more particularly, to a calibration apparatus for calibrating timing mismatch of an edge rotator operating on multiple phases of an oscillator and related calibration method thereof.
With the development of the semiconductor technology, more and more functions are allowed to be supported by a single electronic device. For example, a multi-radio combo-chip product may support a plurality of communication protocols. All of the radio-frequency (RF) oscillators should be properly designed to avoid conflicting with each other. Specifically, good isolation is required, and injection pulling among oscillators of different radios should be prevented. For example, the pulling of one LC-tank oscillator due to the strong harmonic of the power amplifier (PA) output should be avoided; besides, the pulling of one LC-tank oscillator due to a local oscillator (LO) signal or PA signal of another integrated radio should be avoided. Thus, it results in a complicated frequency plan and difficult local oscillator design, especially in analog circuits. In a case where the analog approach is employed, it requires conventional analog blocks such as frequency divider(s) and mixer(s) which limit the frequency offset ratio to a rational number, and requires an LC-tank for unwanted side-band spur suppression which inevitably consumes large area and current.
Thus, there is a need for an innovative non-harmonic clock generator design which may employ a digital realization for generating an output clock having non-harmonic relationship with an input clock through frequency translation, and also employ an autonomous calibration process to compensate for delay mismatch of the non-harmonic clock generator.